The present disclosure relates to a method of removing a metallic material from a cavity of a microelectronic device. More particularly, the present disclosure relates to a method of removing a metallic material employing a chemical solution including an aqueous solution, an oxidizing agent, and a pH stabilizer selected from at least one quaternary ammonium salt or at least one quaternary ammonium alkali.
High gate leakage current of silicon oxide and nitrided silicon dioxide as well as depletion effect of polysilicon gate electrodes limits the performance of conventional semiconductor oxide based gate electrodes. High performance devices for an equivalent oxide thickness (EOT) less than 2 nm require high dielectric constant (high-k) gate dielectrics and metal gate electrodes to limit the gate leakage current and provide high on-currents. Materials for high-k gate dielectrics include ZrO2, HfO2, other dielectric metal oxides, alloys thereof, and their silicate alloys.
In general, dual metal gate complementary metal oxide semiconductor (CMOS) integration schemes employ two gate materials, one having a work function near the valence band edge of the semiconductor material in the channel and the other having a work function near the conduction band edge of the same semiconductor material. A challenge in semiconductor technology has been to provide two types of gate electrodes having a first work function at or near the valence band edge and a second work function at or near the conduction band edge of the underlying semiconductor material such as silicon. This challenge has been particularly difficult because the two types of gate electrodes are also required to be a metallic material having a high electrical conductivity.
In order to provide two types of gate electrodes, portions of a conductive material are removed from one type of gate electrodes while other portions of the conductive material remain in another type of gate electrodes. Removal of such a conductive material needs be performed in a controllable manner. In some cases, removal of a conductive material needs to be performed selective to another conductive material. While the etch chemistry of SC1 etch, which employs a combination of ammonium hydroxide and hydrogen peroxide, is known to etch metallic materials, the etch rate of the SC1 etch is generally high for most metallic materials, and provides insufficient etch selectivity among various metallic materials.
Thus, an etch chemistry that can provide additional selectivity or non-selectivity among metallic materials to overcome the limitations of the SC1 etch is desired.